This invention relates to outdoor lighting controls (OLCs) and particularly to improvements for extending the life span of outdoor lighting controls.
In one type of outdoor lighting control, a normally open alternating current (AC) relay responds to a photosensitive element which acts to open and close current in the relay's contacts on the basis of ambient light conditions and thereby turn on a lamp during the night and turn it off during daylight. At night the photosensitive element limits the current to the relay which closes the relay contacts. This connects the lamp from its power source and turns the light on. During daylight, the photosensitive elements permits higher alternating current to open the contacts. This opens the circuit from the alternating current lines to the lamp and turns the light off in daylight.
OLCs must operate reliably for long periods such as ten years. However, their life span has often been much shorter and their operation unreliable because the relay contacts often exhibit chatter, i.e. rapid opening and closing, as the OLC operation shifts from one condition to another during the change from daylight to night at dusk, and from night to day at dawn. The very slow change in light intensity exacerbates this effect. The repeated opening and closing of the contacts causes them to wear out and the lighting control to operate unreliably. Eventually this reduces the life span of the OLC.